Repeated intratracheal inoculation of house dust mite (Dermatophagoides farinae) induces pulmonary eosinophilic inflammation and IgE antibody production in mice

Background: In vitro studies have shown that the biologic activities of dust mite allergens probably contribute to their allergenicity. However, little is known about their in vivo effect, which may lead to allergic inflammation and sensitization. Objective: In this study we characterized the pathologic and immunologic responses of mice after repetitive challenge with dust mite Dermatophagoides farinae. Methods: Der f crude extract was intratracheally instilled into female BALB/c mice either once or a total of 10 times at 1-week intervals. The inflammatory responses, morphologic changes, IgE antibody and cytokine levels, and costimulatory molecular B7 expression in the airways were then monitored. Results: We demonstrated that single Der f challenge provoked an acute neutrophilic inflammation in the airways. After repeated Der f challenge, there was chronic inflammation characterized by increased numbers of lymphocytes and eosinophils in bronchoalveolar lavage (BAL) fluids. Histopathologically, the numbers of goblet cells and mast cells were significantly increased in the airways of these mice. Repetitive challenge elicited Der f-specific IgE antibody, increased IL-5 and IFN-γ level in BAL fluids, and enhanced costimulatory B7 molecule expression on BAL cells. Conclusions: Our findings are in agreement with those of other in vitro studies concerning the properties of dust mite allergens. Prolonged inhalation of Der f without adjuvant may represent an optimal condition to develop experimental animal models of allergic lung diseases.